This invention relates generally to injection molding and more particularly to a valve gated system having a valve member having a conductive portion at the forward tip end supported by a ribbed insulative portion.
There is an increasing demand for large volume hot runner injection molding systems. This requires large gates and correspondingly large diameter valve members or pins. The problem with large diameter valve members has been that they stick because they conduct too much heat forwardly to the gate. Consequently, the molding cycle has to be slowed down to allow more time for cooling which reduces efficiency and still often leaves unsightly gate marks.
The use of insulative air spaces is well known in the injection molding field. For instance, insulative air spaces are normally provided between a heated nozzle and the surrounding cooled cavity plate. Furthermore, the use of an air space adjacent a conductive plug in a valve pin is disclosed in the applicant's U.S. Pat. No. 4,521,179 which issued June 4, 1985 relating to core ring gate molding. However, in that application there is no concern or requirement for high structural strength because the valve member or pin is not subject to continual impacting when it closes.